In recent years, the popularity of using LEDs in luminaires has increased. In order to obtain cost-efficient solutions, it is common to place several high power and/or medium power LEDs at a certain distance from each other in a luminaire. However, this has as a drawback that the luminaire will have a spotty appearance when in use, due to the irregular illumination pattern caused by the different LEDs.
Further, LEDs sometimes are used with colour converting layers, such as organic phosphor layers, in order to have an output light which is perceived as white by a user although blue LEDs are used. However, when having several LEDs in a luminaire, hot spots may be induced in the colour converting layer, which in the end leads to a reduced lifetime of the luminaire.
There have been attempts to overcome the above drawbacks by introducing diffuser elements in the luminaire in order to spread the light of the LEDs and thereby achieve a more uniform illumination pattern. However, these attempts suffer from reduced system efficiency and increased costs.
CN201779526 discloses a light source which comprises LED chips being fixed to a substrate. On top of each LED chip there is a thin light transmitting layer and on the side surfaces of the LED chip there are inclined structures which refract horizontally emergent light upwards. The disclosed LED light source is inter alia alleged to increase the radiating effect of the LEDs.
Although several attempts have been made to overcome the difficulties above, there is still room for improvements.